Five ESP or Crayon cards are shown in a stand. The performer asks a spectator to select a card while his back is turned, show it to the audience and return it to the stand. When the magician turns around he immediately can tell the spectator the selected card. This can be repeated without any set-up with a second spectator.
There are many different things that you can do with this effect, which is totally self contained and very easy to do. You can use regular cards instead of the ESP cards provided.